CN1054514A

CN1054514A - Frequency response equalizer

Info

Publication number: CN1054514A
Application number: CN91101108A
Authority: CN
Inventors: 维尔纳·海因莱恩
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1990-01-18
Filing date: 1991-01-15
Publication date: 1991-09-11
Also published as: EP0437885A2; EP0437885A3; JPH04212509A; US5121088A; DE4001299A1

Abstract

Frequency response equalizer of the present invention is used in particular for broadband network, and its effect is to reduce the influence of parasitic capacitance to frequency characteristic.The present invention connects one first coil with an electric capacity, a resistance and one second coil, this series connection part is in parallel with a series resistance then, in this circuit, two coils constitute a double wrap coiling transformer, and this transformer comprises two main inductances and two leakage inductances.Suppress two main inductances and two the leakage inductance resistance and the capacitances in series of parasitic capacitance, this cascaded structure is in parallel with this series resistance again, forms a series resonant circuit that works.

Description

Frequency response equalizer

The present invention relates to frequency response equalizer, especially for the frequency response equalizer of broadband network.

In the broadband network such as cable television system, wide-band amplifier is arranged in the cut cable of appointment decays with compensating cable.In these networks, fault in enlargement in desirable level and smooth frequency response may be by the transmission channel of this broadband network in amplification franchise in the frequency response range of each amplifier cause, such fault in enlargement can be compensated by frequency response equalizer.For reaching this purpose, can before each amplifier in transmission channel the attenuation part with pass band damping be set, they self decay can be eliminated in an adjustable frequency range by the additional resonant circuit that is suitable for.A series resistance to be placed on amplifier before to determine the pass band damping amount.This resistance can be connected in parallel with a series resonant circuit, and this series resonant circuit is made up of a resistance, an electric capacity and a coil.The pass band damping amount of locating in resonance frequency (this resonance frequency can be utilized capacitance adjustment) can utilize resistance value to reduce or eliminate to give.The frequency characteristic of such frequency response equalizer can be subjected to the negatory influence of parasitic capacitance such as electric capacity autoeciously, and this is because electric capacity and coil have constituted the cause of an interference resonant circuit autoeciously.It is more little that capacitor volume is wiped in the circuit that shakes in this series connection, disturbs the interference effect of resonant circuit just big more.At the resonance frequency place of series resonant circuit, except desirable the reducing that decay, the undesirable increase of decay has also appearred, especially occur at the higher resonance frequency place.If the amount of this electric capacity electricity is near the value of parasitic capacitance, then disturb the influence of resonant circuit can become also bigger than the influence of this series resonant circuit itself, thereby cause, rather than desirable the reducing of the resonance frequency place of this series resonant circuit decay in undesirable increase of disturbing the decay of resonance frequency place.

The purpose of this invention is to provide a kind of such frequency response equalizer, its parasitic capacitance is lowered the influence of frequency characteristic, and can be used for high frequency.

This purpose realizes by this way, also is about to one first coil, an electric capacity, a resistance and one second coil series connection and is connected in parallel with a series resistance.These two coils constitute a double wrap coiling transformer.

This transformer comprises two main inductances and two leakage inductances.Because main inductance has a high resistance (especially when high frequency) and has suppressed parasitic capacitance basically, so the interference resonant circuit that is made of main inductance and parasitic capacitance can not work.Because the result of transformer double wrap coiling cancels out each other its magnetic flux, eliminating the influence of main inductance, so the work of a series resonant circuit being constituted for connect with this electric capacity and resistance by two leakage inductances of this transformer does not have to influence.So just eliminate the influence of parasitic capacitance, so this frequency response equalizer can use up to the high frequency more than the 650MHZ time.

Referring now to the following drawings illustrated embodiment the present invention is described in more detail:

Fig. 1 illustrates a transmission channel that includes a frequency response equalizer;

Fig. 2 illustrates a transmission channel that includes a frequency response equalizer, and this equalizer comprises a double wrap coiling transformer as shown in the figure;

Fig. 3 illustrates the equivalent circuit diagram of frequency response equalizer;

Fig. 4 illustrates the equivalent circuit diagram that works of frequency response equalizer.

In circuit shown in Figure 1, and a series resistance RS of amplifier V coupled in series is placed between the input E and output terminals A of a transmission channel of cable television system, the input E by a parallel resistance RP earthing potential to adapt to the input resistance of amplifier V, by one first coil L ₁, adjustable resistance R, a tunable capacitor C and one second a coil L ₂The series circuit of forming 1 is in parallel with series resistance RS, coil L ₁, L ₂Be double wrap coiling and mutual inductance coupling high.In the embodiment shown in Fig. 1, coupling constitutes by public iron core K, with iron core K associated coil L ₁, L ₂Constitute a transformer 2, iron core K is made of ferrimagnet.

Series circuit 1 presents a series resonant circuit, and its quality factor can change by adjustable resistance R, and the resonance frequency of series resonant circuit 1 can be determined by tunable capacitor C, because its double wrap coiling, by coil L ₁, L ₂The transformer 2 that constitutes with their magnetic core K comprises two main inductances and a leakage inductance (Fig. 3) of each tool distinct symbols, and this leakage inductance contains leakage inductances two times, and the inductance value of main inductance is more much bigger than the inductance value of inferior leakage inductance.Basically the parasitic capacitance that has suppressed under high frequency, to work especially because main inductance has higher inductive reactance especially when high frequency, therefore the interference resonant circuit that is made of main inductance and parasitic capacitance can not work, thereby can guarantee that this circuit can use when high tremendously high frequency (more than the 650HMZ).Because the double wrap coiling of transformer 2 is cancelled out each other the magnetic flux of two main inductances, that is the symbol difference of two main inductances, so these inductance can not influence the performance of series resonant circuit.Thus, can obtain by electric capacity and resistance (with reference to Fig. 4) and two effective series resonant circuits 1 that inferior leakage inductance is in series and constitutes, this resonant circuit 1 is in parallel with series resistance RS.

Fig. 2 shows a transmission channel that comprises a frequency response equalizer, and emphasis shows the winding construction of the transformer 2 of double wrap coiling among the figure.Fig. 1 describes as reference, and the circuit of being made up of series resistance RS, parallel circuits RP and amplifier V is placed between the input E and output terminals A of a transformer network of cable television system.Coil L ₁, L ₂The top of winding all be connected with series resistance RS, and around the coiling of magnetic core K double wrap.Coil L ₁, L ₂The end of winding all be connected with the series circuit of adjustable resistance R and tunable capacitor.Coil L ₁, L ₂Direction of winding by among the figure shown in the arrow.Though can calculate the value of time leakage inductance LS/2 when adopting the double wrap coiling in very narrow franchise, the iron core body plan is favourable for the diplopore core structure.

Fig. 3 illustrates a transmission channel that comprises a frequency response equalizer, frequency response equalizer wherein is to represent with the equivalent electric circuit of the double wrap coiling transformer 2 of Fig. 1 and Fig. 2, the main inductance LH of this transformer 2 ,-LH is connected with series resistance RS, and connect with two leakage inductance LS/2 respectively, these two times leakage inductance LS/2 interconnects by adjustable resistance R and tunable capacitor C.Parasitic capacitance CP separately be associated in main inductance LH ,-common node and earth potential of LH and inferior leakage inductance LS/2 between.

Very clear and definite, though disturb resonant circuit by main inductance LH ,-LH and parasitic capacitance CP form, but since the material of magnetic core 1 to main inductance LH ,-LH plays the decision influence, disturb the quality factor of resonant circuit to become very low and make, thereby its resonance disturbs inoperative.Because main inductance LH ,-LH also has high inductive reactance when high frequency, so parasitic capacitance CP is inhibited, and eliminate the influence of parasitic capacitance CP, so that frequency response equalizer can use up to the high-frequency more than the 650HMZ time.

Fig. 4 is the equivalent circuit diagram that works of a transmission channel of a cable television system, this cable television system comprises by Fig. 3 with the represented frequency response equalizer of equivalent circuit diagram, and series resonant circuit 1 is composed in series by two leakage inductance LS/2 and adjustable resistance R and tunable capacitor C.As describing referring to figs. 1 through Fig. 3, because two main inductance LH ,-magnetic flux of LH is cancelled out each other, thereby main inductance (referring to Fig. 3) does not influence the performance of series resonant circuit 1.

Claims

1, a kind of frequency response equalizer, the frequency response equalizer in particular for broadband network is characterized in that, one first coil (L ₁) and an electric capacity (C), a resistance (R) and one second coil (L ₂) series connection, this cascaded structure is in parallel with a series resistance (RS) again, this coil (L ₁, L ₂) a formation double wrap coiling transformer (2).

2, frequency response equalizer according to claim 1 is characterized in that: transformer (2) comprise two main inductances (LH ,-LH) and two time leakage inductances (LS/2), (LH ,-LH) effect is cancelled out each other for two main inductances.

3, frequency response equalizer according to claim 1 and 2, it is characterized in that, two leakage inductances (LS/2) of transformer (2) are connected with resistance (R) and electric capacity (C), and this cascaded structure is in parallel with series resistance (RS) again, forms a series resonant circuit that works (1).

4, according to each described frequency response equalizer in the claim 1 to 3, it is characterized in that coil (L ₁, L ₂) have a public iron core (K) by ferromagnetic material.

According to each described frequency response equalizer in the claim 1 to 4, it is characterized in that 5, iron core (K) is made as the diplopore core structure.

According to each described frequency response equalizer in the claim 1 to 5, it is characterized in that 6, resistance (R) and electric capacity (C) are adjustable.